The brain areas which are critically involved in the possible modulation of the immune system by opiates remain unclear. Autoradiographic studies of opiate receptors have provided some information on possible sites of action, but these studies have several limitations, including: (1) the possibility that the receptors may be located on dendritic or axonal processes distal to the cell body; (2) they provide little information about post-receptor events, including gene regulation; and (3) the cells that may be crucial for opiate-immune interaction could be "downstream" from cells bearing the opiate receptor. The activity of cells bearing opiate receptors and those responsive to other immunoregulatory agents, such as IL-1, may converge in cells not bearing opiate receptors. This proposal is designed to address these limitations and to provide information on the anatomical location of opiate and IL-1 responsive cells, as well as information about changes in gene expression that could mediate the modulation of the immune system both by opiates and IL-1. The product of the c-fos proto-oncogene, FOS, is a nucleoprotein. FOS has been shown by our laboratory and others to be opiate inducible. Upon morphine treatment, the presence of FOS is indicated by an intense nuclear immunostain. Immunocytochemistry of the FOS protein has been used by our laboratory and others to map morphine-activated neurons. In this proposal, we intend to apply the same rationale to study the effects of interleukin-1 (alpha, beta) in the rat brain, with and without morphine pretreatment. Morphine and IL-1 appear to induce similar in vivo effects on the endocrine, immune and autonomic systems. Two molecules, FOS and pro- opiomelanocortin (POMC), an opioid peptide precursor, have been chosen as the target proteins for this study. The studies of the c-fos proto- oncogene and its encoded protein, FOS, during IL-1 treatment will provide information on the location of neurons activated or modulated by IL-1 in rat brain. These studies will also explore the mechanisms of IL-1 action through FOS. The POMC gene is expressed in hypothalamic neurons and is a potential target gene for the FOS protein. Numerous studies have demonstrated that POMC is modulated by IL-1 and morphine in anterior pituitary and other peripheral tissues. This study will investigate, at the mRNA and protein/peptide levels, whether POMC is co-regulated by morphine and IL-1 in the rat hypothalamus. The specific aims are outlined as follows: 1. To determine the effects of interleukin-1 (IL-1) treatment on the expression of the c-fos proto-oncogene and the immunoreactivity of FOS protein in rat brain. 2. To determine the effects of IL-1 treatment, after morphine pretreatment, on the expression of the c-fos proto-oncogene, and the immunoreactivity of FOS protein in rat brain. 3. To determine the effects of IL-1 treatment on POMC expression and the immunoreactivity of POMC in rat hypothalamus. 4. To determine the effects of IL-1 treatment, after morphine pretreatment, on POMC expression, and the immunoreactivity of POMC in rat hypothalamus. The experimental techniques involved will be immunocytochemistry, RNA isolation, and Northern and slot blotting analyses. Information from this proposed study will provide an essential anatomical and molecular basis for the possible immunoregulatory effects of morphine on IL-1 action in the central nervous system.